Dermatitis is a general term that describes an inflammation of the skin. Dermatitis can have many causes and occurs in many forms. It usually involves an itchy rash on swollen, reddened skin.

Skin affected by dermatitis may blister, ooze, develop a crust or flake off. Examples of dermatitis include atopic dermatitis (eczema), dandruff, and rashes caused by contact with any of a number of substances, such as poison ivy, soaps and jewelry with nickel in it.

Dermatitis is a common condition that's not contagious and usually isn't life-threatening. Even so, it can make you feel uncomfortable and self-conscious. A combination of self-care steps and medications can help you treat dermatitis.

Each type of dermatitis may look a little different and may tend to occur on different parts of your body. The most common types of dermatitis include:

Atopic dermatitis (eczema). Usually beginning in infancy, this red, itchy rash most commonly occurs where the skin flexes — inside the elbows, behind the knees and the front of the neck. When scratched, the rash can leak fluid and crust over. People with atopic dermatitis may experience improvement and then flare-ups.

Contact dermatitis. This rash occurs on areas of the body that have come into contact with substances that either irritate the skin or cause an allergic reaction, such as poison ivy. The red rash may burn, sting or itch. Blisters may develop.

Seborrheic dermatitis. This condition causes scaly patches, red skin and stubborn dandruff. It usually affects oily areas of the body, such as the face, upper chest and back. It can be a long-term condition with periods of remission and flare-ups. In infants, this disorder is known as cradle cap.

When to see a doctor

See your doctor if:

You're so uncomfortable that you are losing sleep or are distracted from your daily routines

Your skin becomes painful

You suspect your skin is infected

You've tried self-care steps without success

A number of health conditions, allergies, genetic factors and irritants can cause different types of dermatitis:

Atopic dermatitis (eczema). This form of dermatitis is likely related to a mix of factors, including dry skin, a gene variation, an immune system dysfunction, bacteria on the skin and environmental conditions.

Contact dermatitis. This condition results from direct contact with one of many irritants or allergens — such as poison ivy, jewelry containing nickel, cleaning products, perfumes, cosmetics, and even preservatives in many creams and lotions.

Seborrheic dermatitis. This condition may be caused by a yeast (fungus) that is in the oil secretion on the skin. People with seborrheic dermatitis may notice their condition tends to come and go depending on the season.

A number of factors can increase your risk of developing certain types of dermatitis. Examples include:

Age. Dermatitis can occur at any age, but atopic dermatitis (eczema) usually begins in infancy.

Allergies and asthma. People who have a personal or family history of eczema, allergies, hay fever or asthma are more likely to develop atopic dermatitis.

Occupation. Jobs that put you in contact with certain metals, solvents or cleaning supplies increase your risk of contact dermatitis. Being a health care worker is linked to hand eczema.

Health conditions. You may be at increased risk of seborrheic dermatitis if you have one of a number of conditions, such as congestive heart failure, Parkinson's disease and HIV infection.

Scratching the itchy rash associated with dermatitis can cause open sores, which may become infected. These skin infections can spread and may very rarely become life-threatening.

You'll probably first bring your concerns to the attention of your family doctor. He or she might refer you to a doctor who specializes in the diagnosis and treatment of skin conditions (dermatologist).

Here's some information to help you get ready for your appointment and know what to expect from your doctor.

What you can do

Before your appointment, you might want to write a list of answers to the following questions:

What are your symptoms, and when did they start?

Does anything seem to trigger your symptoms?

What medications are you currently taking, including those you take by mouth as well as creams or ointments that you apply to your skin?

Do you have a family history of allergies or asthma?

What treatments have you tried so far? Have any treatments helped?

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to talk about in-depth. Depending on what type of dermatitis you have, your doctor may ask:

Do your symptoms come and go, or are they fairly constant?

How often do you shower or bathe?

What products do you use on your skin, including soaps, lotions and cosmetics?

What household cleaning products do you use?

Are you exposed to any possible irritants from your job or hobbies?

Have you been under any unusual stress or depressed lately?

How much do your symptoms affect your quality of life, including your ability to sleep?

Your doctor may diagnose dermatitis after talking to you about your signs and symptoms and examining your skin. He or she may also suggest doing a skin biopsy or other tests to help rule out other skin conditions.

Patch testing

If your doctor thinks you have contact dermatitis, he or she might conduct patch testing on your skin. In this test, your doctor applies small amounts of various substances to your skin under an adhesive covering.

During return visits over the next several days, your doctor examines your skin to see if you've had a reaction to any of the substances. This type of testing is best done at least two weeks after your dermatitis has cleared up. It's most useful for determining if you have specific contact allergies.

The treatment for dermatitis varies, depending on the cause and each person's experience of the condition. In addition to the lifestyle and home remedies recommendations below, the cornerstone of most dermatitis treatment plans includes one or more of the following:

Exposing the affected area to controlled amounts of natural or artificial light (phototherapy)

These steps can help you manage dermatitis:

Use nonprescription anti-inflammation and anti-itch products. Over-the-counter hydrocortisone cream or calamine lotion can temporarily relieve inflammation and itching. Oral antihistamines, such as diphenhydramine (Benadryl, others), may be helpful if itching is severe. Diphenhydramine may cause drowsiness and slowing of the urinary stream.

Apply cool, wet compresses. Covering the affected area with bandages and dressings can help protect your skin and prevent scratching.

Take a comfortably warm bath. Sprinkle your bath water with uncooked oatmeal or colloidal oatmeal — a finely ground oatmeal that's made for the bathtub. Soak for 5 to 10 minutes, pat dry, and apply moisturizer.

Take a bleach bath. This may help people with severe atopic dermatitis by decreasing the bacteria on the skin. Add 1/2 cup (about 118 milliliters) of household bleach, not concentrated bleach, to a 40-gallon (about 151-liter) bathtub filled with warm water. Measures are for a U.S. standard-sized tub filled to the overflow drainage holes.

Avoid rubbing and scratching. Cover the itchy area with a dressing if you can't keep from scratching it. Trim nails and wear gloves at night.

Moisturize your skin. While your skin is still damp, seal in moisture with an oil or cream. Try different products to find one that works for you. Ideally, the best one for you will be safe, effective, affordable and unscented.

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